1999 E-150 Conversion Van benchseat change
 

Hello I have a 1999 E-150 with captain chairs and the fold out bed bench. The bed bench is never used as a bed and takes up so much room that we decided to try and swap it out with a 4 seater bench and the captain chairs for a 3 seater bench.
I have seen another post with someone who put the 3 seater and bench behind the captain chairs, which would also work..
The new benches I bought include the brackets needed to mount them. So i guess my question is: it seems pretty cut and dry what needs to be done but I am having a tough time pulling the trigger to just rip out the other chairs and drill and mount the new benches down. The van is our primary kid hauler so it cant out of commission for an extended amount of time as i may run into difficulties in this project. any suggestions would be greatly appreciated.
( Ive had the new benches sitting in the garage for about a year now )

Set the seats where you want them WITH the brackets on them.
Align the brackets where they go.
Mark the bolt holes.
Move the seats out.
Cut an X in the carpet with a fresh sharp razor knife with the center of the X exactly in the middle of the bolt hole, about 3" each cut. Fold back the carpet and hold it there so you don't wind it up with the drill.
Drill the hole.
Under the van, point the bolt at the hole. On the bolt put a washer, then a backing plate and stick it up into the hole. Have someone set the bracket onto the bolt, then a washer then a LOCK nut. One of you hold it, the other tightens it.
Repeat until all the bracket are in.

Really not much to it.
When the brackets are tightened down on top of the carpet, the cut lines will not show if you cut them clean enough with a fresh sharp razor knife. If you wind up the carpet in the drill it will likely ruin the carpet.
I recently stripped down a 1998 and this is how the seats were installed. I also had reason to be under my recent 2001 van and all the seats are all held on with backing plates, either bolted directly to the floor for the front buckets or bolted to brackets for the rear benches.

Thanks for your quick reply!
The seats did come with heavy duty brackets the 3 seater bolts down with 4 bolts each bracket and the 4 seater uses 6 bolts per bracket ..but there isnt any kind of plate that goes on the underside as you describe, I see how the plate would reinforce the flooring where the bracket mounts and do want them.. how thick is the plate? can i have it fabricated or can you provide a link to where it can be purchased.
Also, did you have to drop the fuel tank or were able to work around everything..

As I recall there was no issue with the seat bolts near the tank. The seat brackets on mine were mounted far enough outboard to not be above it since the tank is inboard of the frame. Mine was coming apart so taking them out was easy enough, I did it by myself. It was a 1998 E350 15 passenger that had a wheelchair lift in the back so the rear most seats (and the wheelchair lift) were already gone. I couldn't tell you for sure if the upfitter that installed the wheelchair lift put the backing plates on it, but like I said, my 2001 also had them. It was 1/2" steel plate.